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Crystals in Urine: What Calcium Oxalate, Uric Acid and Amorphous Crystals Mean

A few crystals on a urinalysis are usually normal, and many form after the sample leaves the body. Learn how to read the crystal type, the amount and the urine pH together, which crystals always deserve follow-up, how crystals relate to kidney stones, and what to do next.

Published

November 2, 2026

Read time

14 min read

Medically reviewed by

Rhonda Collins, FNP-C

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A few crystals in urine are usually normal. Large amounts of certain types can be a sign of a condition that needs attention, such as a tendency to form kidney stones, a urinary tract infection (UTI) or a problem with metabolism ^[1]. Most crystals on a routine urinalysis come from urine that was briefly oversaturated, from food, or from changes in temperature and pH after the sample was collected ^[2].

The crystal line rarely means much on its own. Three things decide what it means: the type of crystal, how many the lab saw, and the urine pH on the same report. A handful of crystal types, such as cystine, point to a specific diagnosis even when only a few are present ^[3].

What crystals in urine are and why they form

Urine crystals are solid particles that form when minerals or other substances in urine are too concentrated to stay dissolved ^[1]. This usually happens when urine carries high levels of those substances or is too acidic or too alkaline ^[1]. Doctors call the finding crystalluria, and it is a marker of urine supersaturation ^[4].

Supersaturation can come from many places. Inherited diseases, metabolic disorders and medicines can all cause crystals ^[4][5]. So can ordinary causes that MedlinePlus lists ^[1]:

• not drinking enough fluids;
• a diet high in animal protein, such as fish, shellfish and organ meats;
• certain medicines, including calcium-based antacids, some antibiotics, diuretics and antiviral drugs.

Crystals do not always mean something is wrong. Uric acid, calcium oxalate, calcium phosphate and drug crystals can all appear under normal conditions ^[5].

How labs report crystals on a urinalysis

A urinalysis reports crystals from the microscopic exam, by type and amount, not as a concentration ^[1]. The report shows whether crystals are present, what they are made of and how many there are ^[1].

The amount is usually counted per high-power field (HPF), one view through the microscope. On the Quest Diagnostics complete urinalysis, for example, calcium oxalate, triple phosphate and uric acid crystals and amorphous sediment each have their own line, and the reference result for each is “None or Few” ^[6]. A separate line for other crystals has a reference result of “None seen” ^[6]. Words such as rare, few, moderate and many are how the lab describes the count.

Mito’s urine crystals page covers this finding together with casts and mucus, because all three come from the same microscopic look at the urine sediment.

Read the crystal type with the urine pH

Most crystal types form only in a certain pH range, so the pH line on the same report is the best clue to what a crystal result means ^[3][4]. Labs that study crystals measure pH for exactly this reason ^[3]. The pH comes from the dipstick part of the same test; see urine pH and specific gravity.

A mismatch is useful too. Triple phosphate crystals in very acidic urine, or uric acid crystals in alkaline urine, are worth a second look on a fresh sample.

When a routine urinalysis shows no crystal line

Some routine urinalyses only run the microscopic exam when the dipstick finds something, so a report with no crystal line does not always mean no crystals. Labcorp’s routine urinalysis (test 003038) skips the microscopic exam when protein, leukocyte esterase, blood and nitrite are all negative, and reports only the dipstick results ^[10]. Quest’s complete urinalysis always includes the microscopic exam ^[6].

Amorphous crystals in urine

Amorphous crystals are tiny granules with no clear shape, and they are usually a harmless finding that depends on the urine pH and how the sample was stored ^[2][7]. They come in two kinds that look the same under the microscope ^[7]:

• Amorphous urates form in acidic urine. They look like small yellow-red granules ^[7].
• Amorphous phosphates form in alkaline urine. Amorphous calcium phosphate appears when the pH is high, above about 6.6, even when calcium and phosphate levels are normal ^[7].

The pH line on the same report usually tells you which kind you have. When it does not, a lab can tell them apart with a simple solubility test: amorphous urates dissolve with gentle heat, and amorphous phosphates dissolve in acid ^[7].

Amorphous crystals are among the crystals that most often form after urination, as urine cools and its pH changes while it stands ^[2]. Refrigeration can also make phosphates and urates fall out of solution ^[7]. Precipitated phosphate crystals in alkaline urine are a common reason urine looks cloudy ^[8]. For the other causes, see what cloudy urine means.

On a Quest report, this finding appears as “Amorphous Sediment,” with “None or Few” as the reference result ^[6].

Calcium oxalate crystals in urine

Calcium oxalate crystals are the most common crystals behind kidney stones, but a few of them are also a common finding in healthy people ^[1][8]. Calcium oxalate makes up an estimated 40% to 60% of kidney stones ^[7]. Under the microscope, the classic form looks like a small square envelope ^[8].

There are two main forms, and they mean slightly different things ^[3]:

• Calcium oxalate dihydrate (the envelope shape) may point to high urine calcium. It can also form quickly in the sample after collection, so it sometimes reflects only a delay before the sample was examined ^[3].
• Calcium oxalate monohydrate forms when urine oxalate is high. Many monohydrate crystals, or monohydrate crystals without the dihydrate form, strongly suggest very high oxalate excretion, which can come from an inherited condition called primary hyperoxaluria or from bowel disease (enteric hyperoxaluria) ^[3].

Elongated, shuttle-shaped calcium oxalate monohydrate crystals are a recognized sign of ethylene glycol (antifreeze) poisoning ^[3][7].

The everyday causes MedlinePlus lists for large amounts of crystals apply here: low fluid intake, a diet high in animal protein and some medicines ^[1].

Uric acid crystals in urine

Uric acid crystals form in acidic urine, especially at a pH of 5.5 or lower, so the pH on the same report often explains them ^[3]. They are yellow to orange-brown and may look like diamonds or barrels ^[8].

MedlinePlus says large amounts of uric acid and urate crystals can form when metabolic problems such as gout and type 2 diabetes make the urine too acidic ^[1]. Uric acid stones are also seen in people with low urine pH from diabetes or metabolic syndrome ^[3]. Uric acid stones make up roughly 5% to 10% of kidney stones ^[7].

Uric acid crystals in urine are not the same as a high uric acid level in the blood. A blood test measures uric acid itself. For how blood uric acid relates to gout and the kidneys, see uric acid and your joints, kidneys and heart.

Triple phosphate crystals and infection

Triple phosphate crystals, also called struvite or magnesium ammonium phosphate, are the crystal most closely tied to urinary tract infection ^[3][8]. They are colorless and have a typical “coffin lid” shape ^[8].

They form in neutral or alkaline urine, usually above pH 7 ^[3][7]. Bacteria that make the enzyme urease break urea down into ammonia, and alkaline urine in someone with a UTI suggests one of these urea-splitting organisms ^[7][8]. Proteus species are the classic example ^[8]. One review calls struvite pathognomonic for urea-splitting bacteria ^[3]. A clinical review notes that triple phosphate crystals may be normal but are often associated with alkaline urine and UTI ^[8].

Repeated UTIs can cause large amounts of struvite crystals ^[1], and urea-splitting infections can form large branching kidney stones called staghorn calculi ^[8].

Read triple phosphate crystals with the infection lines on the same report: nitrite, leukocyte esterase, white blood cells and bacteria. For how those lines fit together, see what nitrites in urine mean. Mucus is another microscopic finding that often rises with infection; see what mucus in urine means.

Rarer crystals that always need follow-up

A few crystal types point to a specific inherited condition, a medicine or a poisoning, and they are worth taking to a doctor even when only a few are seen.

• Cystine. Flat, hexagonal crystals that form in acidic urine ^[8]. They are specific to cystinuria, an inherited condition that causes recurring stones. Their shape is so typical that the diagnosis is almost certain even when only a few crystals are seen ^[3].
• 2,8-dihydroxyadenine. Round, reddish-brown crystals with a tree-ring pattern ^[7]. They are a sign of a rare inherited enzyme deficiency (APRT deficiency) that can quietly damage the kidneys over time ^[3][7].
• Tyrosine and leucine. These amino acid crystals are much less common and may also reveal an underlying genetic disorder ^[3].
• Drug crystals. Many medicines can crystallize in urine, including high-dose amoxicillin, sulfamethoxazole, ceftriaxone, acyclovir and atazanavir ^[3][4]. Drug crystals can lead to stones or to kidney injury when they form inside the kidney tubules ^[2][3]. If your report mentions a drug crystal, tell the clinician who prescribed the medicine.
• Elongated calcium oxalate monohydrate. As above, these can signal ethylene glycol poisoning ^[3][7].

Labs sometimes need polarized light, a solubility test or infrared analysis to identify unusual crystals ^[4][7].

Crystals in urine vs kidney stones

Crystals always form before a kidney stone does, but most crystals never become stones ^[5]. A stone is crystals that have grown and stuck together into a hard, pebble-like piece in the kidney ^[1]. Most crystals seen on a urinalysis come from normal urine ^[7].

What links crystals to stones is persistence. In one study described in a 2022 review, 204 people who formed calcium oxalate stones were followed for 7 years. Those whose urine showed crystals in at least half of their samples had a stone recur in 87% of cases. Among those with crystals less often, 9% had a recurrence ^[3]. A single result says much less than a pattern over repeated fresh samples.

Other findings on the same report raise or lower the odds. A clinical review advises suspecting a stone when a person has severe pain together with red blood cells, white blood cells and crystals in the urine ^[9]. For blood on the same report, see what blood in urine test results mean.

Kidney stones are caused by high levels of calcium, oxalate and phosphorus in the urine ^[11]. A urinalysis can show blood in the urine and minerals that can form stones, while blood tests and imaging such as a CT scan find the stone itself and its size and location ^[12].

Crystals that form after the sample is collected

Normal urine can grow crystals as it cools, so crystals seen in a sample that sat out or was refrigerated may not have been in your body at all ^[9]. For this reason, only fresh urine should be examined for crystals ^[9].

Several crystal types are especially prone to this:

• Amorphous urates and phosphates. Changes in temperature and pH as urine stands after urination are a common cause ^[2], and refrigeration can make phosphates and urates precipitate ^[7].
• Calcium oxalate dihydrate. It can form quickly in urine outside the body, so a delay before the sample is examined can produce it ^[3].

This creates a real trade-off. Refrigeration is the standard advice when a sample cannot be examined within about two hours, because longer delays make other results unreliable ^[8]. But cold also makes crystals form. Labs that specialize in crystal analysis use the first or second urine of the morning, bring it to the lab in under two hours, keep it at room temperature and examine it without delay ^[3].

If your crystals were seen on a sample that waited, a repeat on a fresh sample is the simplest way to tell whether they are real.

What to do after a crystals in urine result

1. Check the type and the amount. A few common crystals (calcium oxalate, uric acid, amorphous) are usually normal ^[1]. Many crystals, or any of the rarer types above, call for the next steps.
2. Read the pH line. Amorphous urates and uric acid fit acidic urine. Amorphous phosphates and triple phosphate fit alkaline urine ^[3][7]. For more on that line, see urine pH and specific gravity.
3. Read the other lines on the same report. Blood points toward a possible stone. Nitrite, leukocyte esterase, white blood cells and bacteria point toward infection ^[9]. If the same report flags bilirubin, see what bilirubin in urine means.
4. Repeat the test on a fresh sample. Collect a clean-catch sample and get it to the lab promptly, without letting it sit for hours or chill ^[1][9][3].
5. See your doctor if crystals persist or the type is unusual. A doctor can order the stone tests that fit: blood tests, imaging, and sometimes a 24-hour urine collection, which can be more accurate because crystals and other substances in urine vary through the day ^[1][12]. The American Urological Association guideline recommends a screening evaluation for people with a first or recurrent kidney stone, and a fuller metabolic evaluation for selected higher-risk people ^[13].

For people who form stones, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) calls drinking enough liquid, mainly water, the most important thing you can do to prevent kidney stones ^[14]. For everyday habits that support urine health, see how to improve your urine crystals.

The Urinalysis, Complete Test with Reflex to Urine Culture always includes the microscopic exam and reports calcium oxalate, uric acid and triple phosphate crystals and amorphous sediment as separate lines ^[6]. If the results suggest an infection, it runs a urine culture automatically ^[6]. The Urinalysis, Routine Test also covers the dipstick and microscopy, but how much crystal detail you see depends on the lab: at Labcorp, the microscopic exam runs only when the dipstick is positive ^[10].

When to get prompt care

See a doctor right away if crystals in your urine come with symptoms of a kidney stone ^[11]:

• sharp pain in your back, side, lower abdomen or groin;
• pink, red or brown blood in your urine;
• a constant need to urinate, or pain while urinating;
• being unable to urinate, or only passing a small amount;
• cloudy or bad-smelling urine.

Nausea, vomiting, fever and chills can come with these symptoms ^[11]. They may mean a stone or a more serious condition ^[11]. A large stone that blocks the flow of urine can cause pain, bleeding and serious damage to the kidneys ^[1].

References

1. MedlinePlus. Crystals in urine. National Library of Medicine. Last updated December 19, 2024.
2. Fogazzi GB. Crystalluria: a neglected aspect of urinary sediment analysis. Nephrol Dial Transplant. 1996;11(2):379-387. PMID: 8671802
3. Letavernier E, Bazin D, Daudon M. Description of stone morphology and crystalluria improve diagnosis and care of kidney stone formers. Healthcare (Basel). 2022;11(1):2. PMID: 36611462
4. Daudon M, Frochot V. Crystalluria. Clin Chem Lab Med. 2015;53 Suppl 2:s1479-s1487. PMID: 26509782
5. Simhadri PK, Rout P, Leslie SW. Urinary crystals identification and analysis. In: StatPearls. StatPearls Publishing; 2024. NBK606103. PMID: 39163441
6. Quest Diagnostics. Urinalysis, Complete, with Reflex to Culture (test code 3020). Test directory.
7. Lee AJ, Yoo EH, Bae YC, Jung SB, Jeon CH. Differential identification of urine crystals with morphologic characteristics and solubility test. J Clin Lab Anal. 2022;36(11):e24707. PMID: 36164743
8. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. Am Fam Physician. 2005;71(6):1153-1162.
9. Hitzeman N, Greer D, Carpio E. Office-based urinalysis: a comprehensive review. Am Fam Physician. 2022;106(1):27-35B.
10. Labcorp. Urinalysis, Routine With Microscopic Examination on Positives (test 003038). Test menu.
11. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and causes of kidney stones. Last reviewed May 2017.
12. National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of kidney stones. Last reviewed May 2017.
13. Pearle MS, Goldfarb DS, Assimos DG, et al. Medical management of kidney stones: AUA guideline. J Urol. 2014;192(2):316-324. PMID: 24857648
14. National Institute of Diabetes and Digestive and Kidney Diseases. Eating, diet, and nutrition for kidney stones. Last reviewed May 2017.

Frequently asked questions

Are crystals in urine normal?

A few small crystals are normal and usually cause no problems, according to MedlinePlus. Calcium oxalate, uric acid, calcium phosphate and amorphous crystals are all seen in healthy people, and many form only after the sample has cooled or stood for a while. Large amounts of certain types, crystals that keep coming back on fresh samples, and rare types such as cystine are the results that need follow-up.

Do crystals in urine mean kidney stones?

Not on their own. Crystals always form before a stone does, but most crystals never become stones. Crystals matter more when they appear on repeated fresh samples, when you have had a stone before, or when the same report shows blood in the urine and you have pain in your back, side or groin.

Do crystals in urine mean diabetes?

Crystals cannot diagnose diabetes. The link is urine pH: type 2 diabetes and metabolic syndrome can make urine more acidic, and acidic urine favors uric acid crystals and uric acid stones. The glucose line on the urinalysis and blood tests such as HbA1c are the results that speak to diabetes.

Can a UTI cause crystals in urine?

Yes, one type in particular. Triple phosphate crystals, also called struvite, form when bacteria that split urea make the urine alkaline. Proteus is the classic example. Triple phosphate crystals next to a high pH, positive nitrite or leukocyte esterase, or white blood cells point toward an infection and usually lead to a urine culture.

How do you get rid of crystals in urine?

Most crystals need no treatment, and the first step is often a repeat test on a fresh sample. When crystals keep appearing or you form kidney stones, the plan depends on the crystal type and what a stone evaluation finds. The National Institute of Diabetes and Digestive and Kidney Diseases calls drinking enough liquid, mainly water, the most important thing you can do to prevent kidney stones.